British Journal of Radiology (2006) 79, 359-361
© 2006 British Institute of Radiology
doi: 10.1259/bjr/33391462
The angel in the marble
D J A Butteriss, BSc, MBBS (Hons), FRCR
1
M Clarke, FRCS, FRCOphth
2 and
D Birchall, MB, BChir, FRCR
1
1 Department of Neuroradiology, Regional Neurosciences Centre, Newcastle General Hospital, Newcastle upon Tyne, 2 Ophthalmology Department, Royal Victoria Infirmary, Newcastle upon Tyne, UK
Correspondence: Dr D Birchall, Department of Neuroradiology, Regional Neurosciences Centre, Newcastle General Hospital, Westgate Road, Newcastle upon Tyne NE4 6BE, UK.
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Introduction
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A 56-year-old woman presented to the ophthalmology department complaining of subacute painless decrease in visual acuity in her right eye. She had a previous history of longstanding poor visual acuity in the left eye, which had not been formally investigated. No other significant history was elicited. Fundoscopy revealed atrophy of the left optic disc and swelling of the right disc. No other significant abnormality was found.
CT (Figure 1
) and MRI (Figure 2) were performed on this patient. What are the abnormalities? What is the diagnosis in this case? What are the potential causes of optic atrophy in this condition?
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Figure 1. (a) CT shows buckling of the right optic nerve and diffuse calvarial hyperostosis. (b) There is generalized hyperostosis of the skull base. (c) There is bilateral narrowing of the optic canals and superior orbital fissures.
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Figure 2. (a) Axial T2 image shows dilatation of the optic nerve sheath on the right, and optic nerve buckling. Diffuse hyperostosis is again evident. (b) Coronal short tau inversion recovery (STIR) imaging through the orbits confirms optic nerve sheath dilatation on the right, with increased signal within the nerve itself. The left optic nerve is atrophic. (c) More posterior the coronal STIR image shows compression of the optic nerves within the optic canals (arrows). (d) Sagittal T2 image demonstrates skull base and upper cervical hyperostosis, with distortion of the cervico-medullary junction and of the pituitary fossa.
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Imaging findings
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CT demonstrates marked thickening and sclerosis of the calvarium and skull base. The optic canals are stenosed bilaterally, particularly on the left. The right optic nerve is buckled. The intracranial contents are otherwise normal. In the absence of other causes of diffuse hyperostosis, these appearances are consistent with osteopetrosis. MRI shows left sided optic atrophy. On the right, there is dilatation of the optic nerve sheath and increased T2 signal within the optic nerve, appearances consistent with decompensating subacute optic nerve compression at the orbital apex. Sagittal imaging shows clival and skull base hyperostosis with distortion of the medulla and proximal cervical spinal cord, and compression of the pituitary gland.
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Discussion
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Osteopetrosis, also known as Albers-Schonberg disease or marble bone disease, is an uncommon genetic disorder characterized by increased bone thickness and density, and is caused by impaired osteoclast maturation or function resulting in decreased bone resorbtion and modelling. Several forms have been identified, the most common being the infantile autosomal recessive type and the delayed autosomal dominant type. The recessive form is also known as malignant osteopetrosis and presents in early childhood with fractures and the sequelae of pancytopaenia due to marrow space obliteration. Neurological complications are common, and are secondary to raised intracranial pressure (ICP) due to calvarial expansion, and narrowing of the cranial foramina resulting in cranial nerve, spinal cord and vascular compression. The delayed form usually presents in early adulthood, although it demonstrates increasingly early onset in affected familial series. It may be asymptomatic and diagnosed incidentally on radiological investigations, but usually presents with easy fracturing or with neurological complications such as raised ICP or cranial nerve palsies. It is divided into two forms based on radiological and clinical criteria: type 1 demonstrates diffuse calvarial thickening and sclerosis with diffuse sclerosis of the axial skeleton; type 2 has less marked calvarial thickening, but the skull base is more severely affected than in type 1 and there is vertebral endplate sclerosis and bone-within-a-bone appearance [2, 3].
Overall, the most common neurological complication of osteopetrosis is visual loss and optic atrophy. There are three possible causes of visual loss [4]:
- Optic nerve compression secondary to stenosis of the optic canals.
- Papilloedema due to raised ICP.
- Primary retinal degeneration.
In this report, the likely cause of visual loss and optic atrophy is stenosis of the optic canals. The late presentation is an unusual feature of the case.
Secondary optic atrophy is treatable, management dependent on the cause. Optic canal stenosis is treated by orbital deroofing, and papilloedema treated by reducing ICP, either by ventricular shunting, or by craniectomy alone or in conjunction with cranial vault expansion [5].
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Acknowledgments
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Michelangelo, "I saw the angel in the marble and carved until I set it free."
Received for publication May 16, 2005.
Accepted for publication June 27, 2005.
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References
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- Hall CM. International Nosology and Classification of Constitutional Disorders of Bone (2001). Am J Med Genet 2002;113:65–77.[CrossRef][Medline]
- Anderson PE, Bollerslev J. Heterogeneity of autosomal dominant osteopetrosis. Radiology 1987;164:233–5.
- Cure JK, Key LL, Goltra DD, VanTassel P. Cranial MR imaging of osteopetrosis. AJNR Am J Neuroradiol 2000;21:1110–5.[Abstract/Free Full Text]
- Stewart CG. Neurological aspects of osteopetrosis. Neuropathol Appl Neurobiol 2003;29:87–97.[CrossRef][Medline]
- Vanier V, Miller NR, Carson BS. Bilateral visual improvement after unilateral optic canal decompression and cranial vault expansion in a patient with osteopetrosis, narrowed optic canals, and increased intracranial pressure. J Neurol Neurosurg Psychiatry 2000;69:405–6.[Free Full Text]
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Introduction
Imaging findings
